Television receiving system



Nov. 19, 1946.

7 E. J. GORN TELEVIS ION RECEIVING SYSTEM 4 Filed se i. 14, 1944 4Sheets-Sheet 1 NNQQQ NQK Nov. 19, 1946.

E. J. GORN TELEVISION RECEIVING SYSTEM 4 Sheets-Sheet 2 Filed Sept. 14,1944 Nov. 19, 1946. GQRN 2,411,155

TELEVIS ION RECEIVING SYSTEM Filed Sept. 14, 1944 4 Sheets-Slieet s 4 II I, 1 .4, 1, fl/VHLIZER 2 2 I I] J 7 7 2/ a v I 4 22 I /2 i W I scm'E/VI NVE/VTO/f.

Nov. l9, 1946 E. J. GORN 2,411,155

TELEVISION RECEIVING SYSTEM Filed Sept. 14, 1944 4 Sheets-Sheet 4 scenePatented Now- 19, 1946 TELEVISION RECEIVING SYSTEM Elmer J. Gorn,Newton, Masa, assignor to Raytbeon Manufacturing Company, Newton, Mass.,acorporation of Delaware Application September 14, 1944, Serial No.554,059

This invention relates to a television receiving system.

In a television receiving system it is desirable 9 Claims. (01. 88-61)to utilize a receiver screen which will act to mod- Y ulate a light beampassing through it, the modulation varyin from point to point on thescreen in accordance with the intensity values of the received picturesignals so that the light thus modulated may either be viewed directlyor enlarged and projected onto a viewing screen to give a reproductionof the picture.

An object of this invention is to produce a novel screen of theforegoing type utilizing the property of a film of magnetic material torotate the plane of polarization of polarized light passing through sucha film in a strong magnetic field, and in which the magnetic propertiesof the film are varied from point to point in order to recreate areceived picture.

Another object is to produce the above variation in the magneticproperties of the film by bombarding the film-with a beam of electrons.

The foregoing and other objects of this invention will behest understoodfrom the following description of exemplifications thereof, referencebeing had to the accompanying drawings wherein Figs. 1, 2, 3 and 4represent different forms of apparatus embodying my invention.

In the form shown in Fig. l, a cathode ray tube is provided within anevacuated envelope l containing, at one end thereof, a cathode 2 adaptedto beheated to temperatue of thermionic emission by a heating filament3. The electrons emitted from the cathode 2 are controlled by means of acontrol electrode 4, accelerated by a first anode 5 and focused by theelectrostatic fieldiormed between the first anode 5 and the second anode6. The electron beam thus produced is deflected by deflecting coils I orby any other well known deflecting means so as to produce a scanningbeam of electrons 8. The electron beam 8 is directed toward an end wall9 of the envelope I, said end wall being made of suitable clear glass.The end wall 9 is coated on its interior surface with a thin film In ofmagnetic material such as iron. This film is sumciently thin so as tobesubstantially transparent to light. A suitable positive potential may beapplied to the second anode 6 from a terminal I I. The film I 0 maybeelectrically connected to the second anode 6. In some cases it may bedesirable to insert an additional source of voltage I: in the connectionbetween the film l0 and the second anode 6 so as to make the filmsomewhat more positive than said second anode.

In order to create a strong magnetic field through the film II), theenvelope l is surrounded adjacent said film by a coil l3 energized fromterminals H with a suflicient current so as to create as strong amagnetic field as possible with the-lines of flux extendingsubstantially perpendicularly through the film Ill. The coil l3 may beprovided with a suitable external core structure, not shown, so as tomaximize the magnetic field through the film ID.

A strong source of light [5, which may be for example an incandescentlamp, is provided to produce the beam of light to be modulated. Thelight coming from the source I5'is concentrated by an opticalcondenserl6 which thus forms a beam of light II. The beam I1 is passedthrough a, polarizer l8 which allows polarized light vibratingsubstantially in one direction only to pass through it. Therefore, thelight, which comes through the polarizer I8, is polarized in a prethinfilm of magnetic material in a strong magnetic field, the plane ofpolarization of the light will be rotated through a substantial angle.Thus when the polarized lightbeam l1 passes through the film In, itsangle of polarization is rotated. As the beam of light emerges from theend wall 9, it is caused to fall upon an analyzer 20 which permits lightpolarized substantially in one direction only to pass through it. Withno electron beam 8 falling upon the film III, the analyzer 20 may beoriented with its plane of polarization at right angles to the plane ofpolarization of the light coming through the end wall 9. Under theseconditions the analyzer 20 will not pass any of the light and thereforethe beam will be completely extinguished. As an alternative arrangement, the analyzer 20 may be oriented so that its plane of polarizationis parallel with the plane of polarization of the light coming throughthe s end wall 9. Under these conditions the light is free to passthrough the analyzer 20.

The beam of light which passes through the analyzer 20 is projected-bythe. projection lens 2| and is cast as an enlarged image on theprojection screen 22.

When the screen In is bombarded with a beam of electrons of sufllcientintensity, the material of the screen In isexcited to such a degree asto destroy the magnetic properties of the material and render saidmaterial non-magnetic. when this occurs the plane of polarization of thelight passing through the film I is no longer rotated and therefore theplane of polarization of the light falling upon the analyzer 20 ischanged. In case the analyzer has been set for extinction, this changeallows light to pass through whereas, if

the analyzer has been oriented initially so as to allow light to passthrough it, extinction of the light will occur. As the intensity of theelectron beam is reduced or as the beam moves away from an excited spoton the screen 10, that spot quickly loses its excitation and regains itsmagnetic properties. The plane of polarization of the light passingthrough the wall 9 is thereupon restored to its original position andthe initial conditions of passage of light through the analyzer 20 arerestored.

The picture signals which are received and impressed upon the controlelectrode 4 are caused to modulate the strength of the electron beam 8above and below the critical value at which the magnetization of thematerial in the film I0 is destroyed. Thus as the electron beam 8 scansthe film III, the elemental light and dark areas of the desired picturewill be recreated in the film In as non-magnetic and magnetic elementalareas. In the case where the analyzer 20 is initially set forextinction, the non-magnetic elemental areas will correspond to thelight areas of the picture. Conversely, in the case where the analyzer20 is initially set for passage of light, the non-magnetic elementalarea .will correspond to the dark areas of the picture. When themagnetic properties of the film i0 have been modulated as describedabove, the light which comes through the analyzer 20 will representaccurately the received picture values and therefore this picture can beprojected by the lens 2| onto the viewing screen 22.-

In some cases difiiculty may be encountered in securing a sufiicientlyhigh intensity of magnetic field through the film 10 in the arrangementas shown in Fig. 1 so as to produce a maximum I effect. Fig. 2 shows analternative arrangement in which a high intensity of magnetic fieldthroughout the film I0 is more readily obtainable. In Fig. 2 the samereference numerals are applied where the elements are identical withthose in Fig. 1. In Fig. 2 the thin magnetic'filrn 23 is placed upon anend wall 24 of the envelope i, said end wall being located atan angle tothe beam of polarized light I'l passing through it. The magnetic fieldis passed through the film 23 in a direction parallel to the planethereof by means of external magnetic poles 25 and 26. These externalmagnetic poles may be part of a strong permanent magnet or a strongelectromagnet. In order more readily to lead the flux into the film 23,a pair of internal, thickened magnetic poles 27 and. 28 may be mountedwithin the envelope I adjacent the upper and lower,

edges respectively of the film 23. These magnetic poles likewise tend toshield the electron beam 8 against distorting efiects of the externalmagnetic field. By this arrangement very high intensities of magneticfield may be created in the film 23. By passing the polarized light beamI! through the film 23 at an angle thereto, there will be a substantialcomponent of light parallel to the direction of the lines of flux so asto produce the desired rotationof the plane of polarization of the lightas it passes through the film 23. In this arrangement likewisemodulation of the magnetic properties of the film 23 is secured bybombarding said film with the modulated electron beam 3.

An increase in the angle of rotation of the plane of polarization may besecured by the ar rangement shown in Fig. 3. In this figure the samereference numerals are applied where the elements are identical withthose of Fig. 2. In Fig. 3 instead of permitting the polarized lightbeam to pass through the end wall 24, said end wall is provided with areflecting layer 29 which may be, for example, a mirror film of silver.Between the refiecting layer 29 and the thin magnetic film 23 there ispreferably placed a thin layer 30 of a highly dielectric transparentmaterial such as a glass having a high dielectric constant. Thus thelight beam l1 passes through the film 23 and the layer 30 whereupon itis reflected from the layer 29 back through the layers 30 and 23. Thereflected light emerges from a lower wall 3| of the envelope I, saidlower wall being made of suitable clear glass. The analyzer 20, the lens2i and the screen 22 are placed in the path of the beam l1 as itemergesfrom the lower wall 3|. I

The action of the .system shown in Fig. 3'ls substantially identicalwith that of Fig. 2 except that an increased effect may be secured by anincrease in the rotation of the plane of polarization which is producedwhen the magnetic properties of the film 23 are present.

In the embodiment illustrated in'Fig. 4 the I same reference numeralsare applied Where the elements are identical with those of Fig. 3. InFig. 4 there is provided a magnet 32 sealed in the wall of the envelopeI. This magnet may be carried by a sealing ring 34 whose edges 33 aresealed to the-glass of the envelope I. The magnet 32 may be providedwith a strong magnetic field by means of a suitable energizing coil 36.Of course it is to be understood that the magnet 32 could be 'apermanent magnet if so desired. The magnet 32 is provided with apolished pole surface 35 which carries the dielectric layer 30 andthe'thin magnetic film 23 as described in Fig. 3. In Fig. 4 the.polarized light beam I1 is passed through the film 23 and the layer 30and then is reflected from the polished pole face 35in a manner similarto that described in connection with Fig. 3.

oriented that the electric vector thereof is either parallel orperpendicular to the plane of the pole face 35, such a rotation will notoccur. Therefore, the polarizer I8 is so oriented that when the magneticproperties of the film 23 are destroyed, the plane of polarization ofthe incident light on the pole face 35 has its electric vector eithersubstantially parallel or substantially perpendicular to the pole face35. Such a relationship will be termed non-rotative in the specificationand claims herein. However, the parallel relationship of the electricvector is preferred to the perpendicular relationship. With the abovenon-rotative orientation of the electric vector, when the magneticproperties of the film 23 arerestored, the film will rotate the plane ofpolarization of the incident light beam I1 and in this way the electricvector will likewise be rotated out of its non-rotative relationshipwith respect to the pole face 35. Thereupon the reflection of the lightbeam II from the pole face 35 will introduce an additional rotation ofthe plane of polarization which will be added to the rotation producedby the film 23. With such an arrangement, therefore, the difierencebetween the angular positions of the plane of polarization when the film23 is magnetic and when it is nonmagnetic is increased. This produces anincreased difierential between the light and dark portions of thereproduced picture.

In the arrangement of Fig. 4 it is to be understood that the magnet 32may be configured in any convenient way so that the pole external to theenvelope I may be located to intensify the magnetic field passingthrough the film 23 and likewise to configure the magnetic field withthe envelope I so as to produce a minimum of disturbances in thescanning of the film 23 by the electron beam 8.

Of course it is. to be understood that this invention is not limited tothe particular details as described above inasmuch as many equivalentswill suggest themselves to those skilled in the art. For example therepresentation of the means of producing the electron beam 8 and thescanning thereof is intended to be purely diagrammatic and in manyinstances it will be found desirable to substitute other types ofscanning arrangements. It is accordingly desired that the appendedclaims be given a broad interpretation commensurate with the scope ofthe invention within the art.

What is claimed is:

1. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means for creatinga magnetic field through said film to rotate the of polarization of saidlight; and means for altering the magnetic properties of said film,whereby the angle through which said plane of polariza tion is rotatedmay be varied.

5. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means forrefiecting said light whereby it passes through initial plane ofpolarization of said light; and

means for altering the magnetic properties of said film, whereby theangle through which said plane of polarization is rotated may be varied.

2. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means for creatinga magnetic field through said film to rotate the initial plane ofpolarization of said light; and means for altering the magneticproperties of said film by bombarding the same with an electron beamwhereby the angle through which said plane of polarization is rotatedmay be varied.

3. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means for creatinga magnetic field through said film to rotate the initial plane ofpolarization of said light; and means for altering the magneticproperties of said film by scanning the same with an intensitymodulatedelectron beam, whereby the angle through which said plane ofpolarization is rotated may be varied.

4. In combination: a transparent film of magnetic material; means forpassing a. beam of polarized light through said film; meansforrefiecting said light whereby it passes through said film a secondtime; means for creating a magnetic field through said film to rotatethe initial plane said film a second time; means for creating a magneticfield through said film to rotate the initial plane of polarization ofsaid light; and means for altering the magnetic properties of said filmby bombarding the same with an electron beam, whereby the angle throughwhich said plane of polarization is rotated may be varied.

6. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means forreflecting said light whereby it passes through said film a second time;means for creating a magnetic field through said film to rotate theinitial plane of polarization of said light; and means for altering themagnetic properties of said film by scanning the same with anintensity-modulated electron beam, whereby the angle through which saidplane of polarization is rotated may be varied.

7. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means for creatinga magnetic field through said film to rotate the initial plane ofpolarization of said light; said last-named means being provided with ahighly polished surface disposed at the rear 01' said film whereby theplane of polarization of said light is further rotated, and said lightis passed through said film a second time; and means for altering themagnetic properties of said film, whereby the angle through which saidplane of polarization is rotated may be varied.

8. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means for creatinga magnetic field through said film to rotate the initial plane ofpolarization of said light; said last-named means being provided with ahighly polished surface disposed at the rear of said film whereby theplane of polarization of said light is further rotated, and said lightis passed through said film a second time; and means-for altering themagnetic properties of said film by bombarding the same with an electronbeam, whereby the angle through which said plane of polarization isrotated may be varied.

9. In combination: a transparent film of magnetic material; means forpassing a beam of polarized light through said film; means for creatinga magnetic field through said film to rotate the initial plane ofpolarization of said light; said last-named means being provided with ahighly polished surface disposed at the rear of said film whereby theplane of polarization of said light is further rotated, and said lightis passed through said film a second time; and means for altering themagnetic properties of said film by scanning the same with anintensity-modulated electron beam, whereby the angle through which saidplane of polarization is rotated may be varied.

ELMER J. GORN.-

